Will bottom composition/hardness maps be accurate in very shallow water (<10')? I have not tried them with ReefMaster but did with Insight Genesis and they were very poor with some users suggesting that the water was too shallow. It seems that might be a valid answer since the sonar signal cone is so small in shallow water that perhaps there is too much noise to get a consistent botto composition? Just wondering if I'm trying to do something that can't be done reliably.